1. Field of the Invention
This invention is concerned with medical catheters and cannulae, and in particular is concerned with a coupling device for connecting a cannula or catheter to a connection tube through which liquid to be administered to a patient is delivered or fluid to be taken from a patient is collected.
2. The Prior Art
A form of coupling which has been in widespread use for many years comprises a female member fixed to the catheter end and having a moulded plastic hub defining an inwardly tapering frustoconical socket, and a male member which is fitted to the end of a connection tube forming part of an administration set for example, and which includes a tapering frustoconical spigot of complementary form to the hub socket for engaging therein with a friction fit. The coupling is made by pushing the male and female members together and is disconnected by pulling them apart. In order to help prevent unintentional disconnection it is known to equip the male member with an internally threaded cap which can be screwed onto a flange provided at the free end of the hub of the female member.
In WO 95/22369 there are described several improvements to medical cannulae couplings aimed at overcoming drawbacks inherent in the known coupling described above, especially regarding the dangers of air embolism should the coupling become unintentionally disconnected, and infection due to bacterial colonisation of the coupling. With the same basic objectives in mind the present invention is concerned with further improvements to medical cannulae couplings.